Zero current, auto exhausting, vacuum circuit interrupter



Sept. 12, 1950 w. 5. PAUL ZERO CURRENT, AUTO EDKHAUSTING vAcuuI CIRCUITINTERRUPTKR 3 Sheets-Sheet 1 Pilot! Sept. 15, 1948 Inventor: William E.Paul,

His Attorney.

Sept. 12, 1950 w. E. PAUL 2,522,236

- zmo cumm'r, AUTO manusnm,

vacuum cmcurr mmnur'rm Filed Sept. 15, 1948 3 Sheets-Sheet 2 I hventorWilliam E. Paul,

His Attorney.

Sept. 12, 1950 w. E. PAUL mo cunxsu'r, AUTO mus'rmc, vncuuu cmcurr mmnumFiled Sept. 15, 1948 3 Sheets-Sheet 3 Invet or: wnnam E. Paul,

His Att orrwey- Patented Sept. 12, 1950 ZERO CURRENT, AUTO EXKAUSTING,VACUUM CIRCUIT IKTERRUPTER William E. Paul, Schenectady, N. Y., assignorto General Electric Company, a corporation of New York ApplicationSeptember 15, 1948, Serial No. 49,376

14 Claims.

This invention relates to electric circuit breakers and moreparticularly to a method and apparatus for drawing an arc. to beextinguished in a vacuum. Where inflammable gases are likely to bepresent, such as in mines or explosive manufacturing plants, it isdesirable that circuit interrupters be provided which would completelyisolate the are from the surrounding atmosphere so that fires andexplosions due to ignition of these gases by the arc would be prevented.Also, where space is limited and where potential hazards due to firesexist, such as in seagoing vessels and in aircraft, it is vital thatsuitable circuit breakers be provided which will guard against suchhazards.

Heretofore, attempts to provide suitable vacuum-type breakers haveinvolved cumbersome and expensive vacuum-maintaining apparatus whichfunctioned as auxiliary equipment to the circuit breaker itself.Maintenance costs as well as initial costs for such equipment havegenerally proved prohibitive. Furthermore, the evolution of profusemetallic and other vapors within the arcing chamber due to the eflect ofthe are on the contacts has caused breakdown of such breakers where themagnitude oi the current is large. Also, as pointed out in the W. K.Rankin Re-issue Patent No. 21,087, which is assigned to the sameassignee as the present invention, the interrupting ability of a vacuumswitch is limited because of the emission of ionized metallic vapor fromthe cathode spot on the parted contacts if the switch opens at theinstant when an appreciable instantaneous value of current is flowingtherethrough.

A principal object, therefore, of my invention is the provision of avacuum-type circuit interrupter wherein the breaker structure itself isadapted to produce a vacuum within the interrupting' chamber each time acircuit interrupting operation is performed thereby necessitating noauxiliary vacuum producing equipment.

Another object of my invention is to provide an improved self-containedinterrupter wherein the arc is completely isolated at all times from thesurrounding atmosphere. Still another object of my invention is theprovision of an alternating current vacuum-type interrupter adapted topart its contacts at the zero point of the alternating current wave inorder that large quantities of vapor will not be produced within theinterrupting chamber during interruption.

A further object of my invention is to provide an interrupter which isparticularly adapted for high current and relatively low voltageapplications and which requires no liquid or gas blast to aid inperforming the interrupting operation.

Further objects and advantages of my invention will become apparent asthe following description proceeds and the features of novelty whichcharacterize my invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

For a better understanding of myinvention, reference may be had to theaccompanying drawings in which Fig. 1 is a side view partially insection showing schematically one embodiment of my invention wherein thecontacts are shown in the closed position; Fig. 2 is a view similar toFig. 1 wherein the various parts are shown in the positions which theyoccupy just after the breaker has completed an opening operation; Fig. 3represents schematically a modification 0f the arrangement shown inFigs. 1 and 2; while Figs. 4, 5, and 6 show diagrammatically the variousparts of Fig. 3 in the closed, opening, and fully opened positionsrespectively.

In accordance with my invention, which is an improvement over thevacuum-type circuit interrupter disclosed in the above Rankin patent, Iminimize or eliminate the generation of metallic or other objectionablevapors by the steps of just ensuring that the interrupting contacts aresurrounded by a vacuum and thereafter causing the contacts to separateeither at or near a current zero of the alternating current circuitcontrolled by the switch.

With reference to Fig. 1, a circuit interrupter embodying my inventionis shown in which the retractable contacts I and 2 are disposed withinthe interrupting chamber 3 filled with liquid, such as mercury, water,carbon tetrachloride, or other suitable material. The chamber 3comprises a metallic closure member 4 and an annular metallic member 5to which the closure member 4 is secured as by welding so as to form afluid-tight seal. Disposed within the annular metallic member 5 is apair of relatively large openings 6 through which the relatively smallcontact rods I and 2 are slidable. Mounted about each of the contactrods i and 2 is a Sylphon bellows 1 constructed of rubber or othersuitable, yieldable, insulating material. The bellows I are sealed in afluid-tight manner to the annular member 5 at their outer ends and tothe contact rods l and 2 respectively at their inner ends. If desiredthe bellows I could be constructed of-metal and the annular member 5could be constructed of suitable sturdy insulating material. The closuremember 4, of course. could be constructed of insulating material. TheSylphon bellows 8 is secured by a fluid-tight seal to the lower edge ofthe annular member 5 so that the space within the bellows 8 isconiinuous with the space enclosed by the annular member 5 and theclosure member 1. The bellows 2 may be constructed of any suitablematerial but preferably should be of metallic construction in order towithstand the various forces applied thereto during the operation of thecircuit breaker. The lower extremity of the bellows 8 is constructed ofa relatively sturdy metallic closure member 9 on which is mounted thesole noid armature l9. Disposed about the lower extremity of the armaturI0 is an operating sole noid coil ll. Should objectionable vaporpressure tend to build up within the interrupting chamber, cooling meansof a conventional type may be utilized to minimize this tendency. Whencoil H is energized, as by closing the manually operable switch l2 or bythe equivalent energizetion of relay [3 by current transformer H uponthe occurrence of an excessive current condition through line IS, thearmature l 0 will move downwardly and hence will elongate the bellows 8,inasmuch as the interrupting chamber 3 is mounted on a fixed supportingstructure not shown. This elongation of the bellows I increases thevolume of the space inside the bellows and the liquid within theinterrupting chamber promptly assumes a lower level due to the action ofgravity thereon. Downward displacement of the liquid creates a vacuum inthe upper portion of the interrupting chamber in the region surroundingthe contacts I and 2, as best seen in Fig. 2. Because this armaturemovement also effects the opening of the contacts, it will be seen that,in accordance with my invention, means operable by the breaker operatingmechanism are utilized to establish a vacuum about the contacts eachtime a circuit interruption is performed, and that by this constructionall the advantages which are to be obtained by utilizing a vacuum-typeinterrupting chamber are achieved without the necessity for usingseparate auxiliary vacuum maintaining apparatus, such as pumps and thelike. Also, as will become evident, difficulties of sustaining a vacuumover long periods are eliminated, for the vacuum need be maintained onlyduring the interrupting process.

As is known in the art, the ability for vacuumtype breakers to withstandthe recovery voltage following an interrupting operation is due to thefact that, because of the vacuum, the arc is not produced in an easilyionized or combustionsupporting medium such as is the case in oil or aircircuit breakers. This advantageous feature is partially offset,however, by the fact that the interrupting chamber is completelyenclosed, and hence, the ionized metallic vapors or gases which areliberated from the contacts due to the action of the are are retainedwithin the interrupting chamber and of necessity will tend to weaken thedielectric strength of the space between the separated contacts. Theextent to which these undesirable metallic and gaseous vapors aregenerated is largely determined by the magnitude of the currentinterrupted. Thus, particularly for alternating current vacuum-typebreakers, it would be advantageous to provide means for parting thecontacts at or near the zero point of the alternating current wave sothat the liberation of ionized gases is thereby reduced to a practicableminimum.

To this end I have provided suitable means for selecting a point at ornear the zero point of the alternating current wave as the particularpoint when the contacts are to be parted. For example, the zero selectorunits generally designated by the numerals l6 and H may be employed.These units l6 and H as such are identical with the zero selector unitsdisclosed and claimed in my Patent 2,436,665 granted February 24, 1948,and assigned to the same assignee as this application. However, forconvenience, a description of these units is recapitulated here. Each ofthe structures l6 and I1 comprises an insulating supporting member 18which is pivotally mounted at the fixed fulcrum l9. Because units it andIl are identical, unit IE only will be described. With reference to unitIS, an oval coil wound from flat copper strip indicated by dotted linesand designated by the numeral 22 is supported within the member I8. Oneterminal of the coil 20 is connected as indicated at 2| via the pivotpin [9 to the circuit controlled by the breaker, while the otherterminal of the coil 20 is connected to the lower end of a relativelystiff but resilient contact carrier arm of conducting material 22. Thearm 22 is rigidly fastened at its lower end into support ll but ispermitted by mechanical deflection of the upper end within anappropriate oval cone space within the coil 20. Accordingly, the unit 16may be pivoted a few degrees counterclockwise about the pin is withoutnecessitating a corresponding movement to the left of contact I which ismounted and electrically connected at the upper end of the resilient arm22. Thus, it will be seen that the circuit through the interruptercomprises the line IS, the coil 20, the contact arm 22, contacts I and2, through unit ll in the same manner as in unit I6, and isolativeswitch 23 to line 24. The arm 22 is held in the closed position shown inFig. 1 by the latch 25 which is pivotally mounted to the fixed pivot 26.A suitable compression spring 21 exerts a turning moment on the latch 25so as normally to maintain the latch in engagement with th cooperatingarm 22, as well as biasing the pivoted units IE or H inwardly.

The selector units [6 and i1 operate to select contact opening at a zeropoint of the alternating current wave because of the interaction ofmagnetic forces exerted between the coils 20 and the arms 22 whichforces are strong enough to maintain the contacts I and 2 in engagementagainst a contact opening force provided the instantaneous currentthrough coil 20 is of sufficient magnitude. More specifically, at aparticular instant, incoming current from line Ii would flow upwardly inunit ii in those portions Of coil 20 which are to the right of contactarm 22 and downwardly in those portions of coil 2| which are to the leftof arm 22 while current in arm 22 would flow upwardly. Thus, inaccordance with well-known principles, an attractive force would beexerted between the arm 22 and the right-hand side of coil 20 and arepulsing force would be exerted between the arm 22 and the left-handside of coil 20. This attraction and repulsion between the coil 22 andthe arm 22 will result in a force which tends to rotate the selectorunit ii, for instance, in a counterclockwise direction about the pivotII and also causes a moment to be exerted on the arm 22 which tends tocause this am to move clockwise asaaaae about its lower end which, aspointed out above. is fixed while the upper end thereof is capable oflimited movement from right to left. With the latches 26 of units I6 andI! in engagement with the flexible arms 22, the contacts I and 2 aremaintained in engagement. The magnetic forces between the strips 22 andthe coils 26 of units It and I! probably would not be sumcient to tripthe latches 26 by forcefully rotating selector units against projection25a of the latch 23 under ordinary fault current conditions. For thisreason mechanical means to be described hereinafter are provided to tripthe latches 25 coincident with the outward rotation of the selectorunits. When selector unit I6, for example, is rotated counterclockwiseabout pivot I2 by mechanical means, the latch 26 is moved out ofengagement with the arm 22 due to forcible engagement between unit I6and projection 26a of the latch 25. The magnetic force tending to rotateunit I6 counterclockwise and the strip 22 clockwise will tend tomaintain contacts I in engagement withcontact 2, while the mechanicalforce rotating unit I6 counterclockwise will bow the arm 22 since theupper end of the arm is fixed in position by the latch 25. If theinstantaneous current is above a predetermined value, the contacts willbe held in engagement but if the instantaneous current is below apredetermined value, the bowed arms 22 will snap apart and separate thecontacts. Thus contacts I and 2 are caused to separate at or near thezero point of the alternating current wave.

For the purpose of causing the selector units I6 and Il to move in thecontact opening direction by mechanical means referred to above, a pairof side links 23 are provided which are secured to the closure member 9at their lower ends and which at their upper ends are provided with alost-motion slot 23. Cooperating with each slot 29 is a pin 30 whichforms the knee of toggle means comprising the links 3I and 32 which arepivotally connected at 33 and 34 to the selector units I6 and I1respectively.

When a, short circuit occurs to produce automatic tripping, the relay I3will be actuated by current transformer I4 in a well-known manner toenergize the solenoid I I. Energization of solenoid II will pullarmature I downwardly which in turn will elongate the bellows 8 andestablish a vacuum within the fixed upper portion of the interruptingchamber as already explained. Continued downward motion of armature IIIthen causes lost motion slots 29 to pick up the pin 36 at the knee ofthe toggle comprising the links 3i and 32. Further downward motion ofthe armature I0 causes the toggle links 3I and 32 to rotate or tilt theselector units I6 and I1 outwardly. When these units engage the latchextensions 25a, the arms 22 and their contacts I and 2 will be freed tospring apart to their open position in the vacuum as soon as theinstantaneous value of the alternating current approaches or is at orbelow the predetermined value as already explained.

It is preferable that means be provided to prevent separation of thecontacts before the liquid has assumed a level well below the contacts.To this end a stop member 36 may be disposed below the armature III forproducing a brieii pause in the solenoids operating stroke. Stop member36 is provided with an armature 31 which cooperates with a solenoid coil36. A compression spring 39 biases the armature 31 and stop member 36 tothe position shown against the fixed stop 46. The stop 33 is spaced fromthe lower end of the armature It a, distance approximating the length ofthe lost motion slot 23 in the upper end of the links 23. After apredetermined downward opening movement of the armature It to lower theliquid level, stop 36 will be encountered before any movement has beenimparted to the selector units I6 and I1 by the toggle links 3I and 32.Thus a vacuum is formed about the contacts I and 2 before the selectorunits I6 and II can move to release the latches 26.

In order to move the stop 36 after an appropriate pause out of the pathof movement of the armature III, a time-delayed relay 4Ia is providedwhich will not operate to close its contacts until a predetermined timeafter the energization of solenoid II. At the end of the pause, therelay 4Ia will close its contacts and will thus energize coil 33 whichin turn will move the arms.- ture 31 and stop 36 to the right to permitarmature III to complete its downward opening travel. It will beappreciated that any equivalent temporary stop means, e. g., a dashpot,could be employed in place of the above-described magnetic stop forensuring any desired delayin effect dur-. ing the breaker openingstroke. As the armature Ill completes its downward travel, the selectorunits I6 and I1 will be rotated outwardly about the fixed pivots I9 tocomplete an interrupting operation by the contacts I and 2 as explainedabove.

After the circuit is interrupted, the breaker will recloseautomatically. This reclosing operation is accomplished by the springaction of the bellows 3 and also by the vacuum in the upper end of thearcing chamber. After the links 3i and 32 break their toggle springs 21will aid in completing the reclosing operation.

Because the circuit breaker embodying my invention reclosesautomatically after an interrupting operation, suitable means must beprovided for isolating the circuit. To this end the actuating lever Hand link 42 are provided which constitute an operating linkage betweenthe armature I0 and an isolating switch blade 23 arranged in series withthe interrupting device. Thus, when armature Ill nears the end of itsdownward circuit breaker opening movement, the lower end thereof willengage the lever 4I to swing it downward about its pivot 43 therebyrotating the switch blade 23 about its fixed pivot 44 to the openposition from its terminal stud 45 as shrown in Fig. 2.

In order to reclose the isolating switch 23, an armature 46 and a coil41 may be provided. Energization of manually operable switch 48 willcause armature 46 to move upwardly against the arm H to close theisolating switch blade 23 thereby re-establishing contact between theblade 23 and the terminal stud 45. The isolating switch comprising theblade 23 and the terminal stud 45 is shown schematically as aconventional airbreak disconnect, although it will be understood thatthis isolating switch might assume equivalent appropriate forms such,for example, as an oil immersed or other totally enclosed disconnectingunit arranged for operation in accordance with the opening stroke of thearmature II).

It will be apparent from the above description that the speed of theinterrupting operation will be limited by the time required for gravityto displace the fluid within the arcing chamber 3 down to a safe levelbelow the contacts I and 2 before permitting them to separate. Thus, in

asaaase order to reduce the duration of the circuit interruptingoperation, it may be desirable to cause the contacts I and 2 to emergefrom the liquid and to form the vacuum at an acceleration greater thanthat due to gravity by exerting an upward pull on the upper end of thearcing chamber, rather than upon the lower end as in Fig. 1, while thelower end of the arcing chamber comprising the bellows 8 would remainfixed in position. If desired, the lower end could be arrangedsimultaneously to move downwardly. In this way the time required toestablish a suitable vacuum around the contacts I and 2 would not belimited by the acceleration due to gravity. An arrangement adapted todecrease the interrupting time in accordance with these principles isshown schematically in Figs. 3-6 and represents a modification of myinvention.

The elements of Fig. 3 which correspond to the elements of Figs. 1 and 2are designated by the same numerals. In the arrangement of Fig. 3, thelower end of the bellows 8 is secured to a fixed support 50. Theinterrupting chamber 3 is shackled for upward movement by some suitablemeans such as a pair of lugs 5I attached thereto and the cooperatingyoke or beam 52. Pivotally connected at either end of the beam 52 is adownwardly extending push rod 53, the lower ends of which are pivotallyconnected to a pair of mutually operable levers 54 which in turn aremounted on the fixed pivots 55. The slotted inner ends of the levers 54are coupled to the crosshead pin 55 which is secured to and hencemovable with the armature extension 51. The outwardly extending ends ofthe levers 54 are coupled to the levers which are coupled to selectorunits I6 and IT at 60. Thus, it will be seen that energization of coil II will cause armature Ill and armature extension 51 to move downwardlythereby elevating the upper end of the arcing chamber due to the actionof the levers 54, while simultaneously elevating the selector units I8and I1 through the corresponding action of the levers 58.

For the purpose of guiding the selector units I6 and Il during theirvertical travel, the rollers GI and 62 are provided. Rollers 6| aremounted on fixed supports whereas rollers 62 are mounted on the selectorunits and are arranged to roll up along the fixed inclined surfaces 63for producing the outward tilting action required by the units I6 and I!as explained in the case of Fig. 1.

Because during the opening operation the selector units I6 and ll ofFig. 3 move vertically, different latches than of Fig. 1 must be used toaccommodate such movement. To this end the latch members 64, mounted tofixed pivots 65, cooperate with the pair of vertical auxiliary latcharms 66, the lower ends of which are mounted on fixed pivots 61. Thelatch arms 65 and the latches B4 are biased to their latching positionas shown by their respective compression springs 68 and II. The contactsI and 2 are provided at their outer ends with rollers 69 which arearranged to track along the parallel latch arms 66. Thus, as selectorunits I6 and I! move upwardly during an opening operation from theposition shown in Fig. 4 to the position shown in Fig. 5, contacts I and2 are maintained in engagement because the rollers 69 are travellingalong the vertical parallel paths provided by the fixed arms 66 eventhough the selector units themselves are tilting outwardly due to thedivergent path of rollers 62 up on the inclined surfaces it. During thisinitial travel of the selector units It and II, the resilient contactarms 22 are bowed inwardly within their respective coils in preparationfor their zero-selecting separating movement as shown in Fig. 5. After apredetermined upward travel of the selector units It and I1, a trippingshoulder 12 provided on each of the selector units engages acorresponding projection 10 of each latch 64 thereby causing the latterto release the contact-holding auxiliary latch arms 55 so that thecontacts I and 2 can snap apart at the next current zero as illustrateddiagrammatically in Fig. 6. This interrupting portion of the openingoperation will be followed by the final sequential isolating portion asexplained in the case of Fig. l. I

In view of the above description of the arrangement shown in Figs. 3 to6, it is clear that the speed of the interrupting operation is notlimited to the speed of travel of a freely falling body because thevacuum is established by mechanical means independent of gravitationalconditions. With this construction a time-delayed relay for delaying theinstant of tripping until after the vacuum is established is notnecessary.

The coils 20 of the selector units I6 and II also serve as magneticblowout means to aid in extinguishing the are drawn between contacts Iand 2. Assuming that the instantaneous current is flowing into theinterrupter from the line I5 of Fig. 1, for example, the magnetic fieldwould be in a direction from the rear to the front of coils 20 and fromfront to rear across contacts I and 2. With current flowing from contactI to contact 2 an upward force would be exerted on the contacts. Uponseparation of contacts I and 2 the are drawn therebetween would be blownupwardly by the magnetic field. With the reversal of the instantaneouscurrent, i. e., when flowing to the interrupter from line 24, themagnetic field across the contacts I and 2 and the direction of currentflow would both reverse simultaneously so that the are still would beblown upwardly.

While I have shown and described particular embodiments of my invention,it will be obvious to those skilled in the art that various changes andmodifications may be made without departing from my invention in itsbroader aspects and I, therefore, intend in the appended claims to coverall such changes and modifications as fall within the true spirit andscope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electric circuit breaker comprising a deformable substantiallyfluid-tight interrupting chamber, a liquid in said chamber, a pair ofrelatively movable interrupting contacts disposed within said chamber,means operable during a circuit opening operation for deforming saidchamber to increase the volume therein so as to form a vacuum in theregion of said contacts and above the level of said liquid, and meansfor separating said contacts after the formation of the vacuum.

2. An electric circuit breaker comprising a substantially fluid-tightinterrupting chamber constructed of deformable material, a liquid insaid chamber substantially filling said chamber under normal conditions,a pair of relatively movable contacts disposed in the upper end of saidchamber and normally immersed in said liquid, means operable in responseto the initiation of a circuit opening operation for elongating saidchamber so as to form a vacuum in the upper end thereof above the levelof said liquid in the region surrounding said contacts, and means forseparating said contacts after the formation of the vacuum.

3. An alternating current electric circuit breaker comprising asubstantially fluid-tight interrupting chamber constructed of deformablematerial, a liquid in said chamber substantially fllling said chamberunder normal conditions, a pair of relatively movable contacts disposedin the upper end of said chamber and normally immersed in said liquid,means operable in response to the initiation of a circuit openingoperation for elongating said chamber so as to form a vacuum in theupper end thereof above the level of said liquid in the regionsurrounding said contacts, and means including a pair of selector unitsoperable after a predetermined elongation of said chamber for separatingsaid contacts at a predetermined point on the alternating current wave.

4, An alternating current electric circuit breaker comprising asubstantially fluid-tight interrupting chamber constructed of deformablematerial, a liquid in said chamber substantially filling said chamberunder normal conditions, a pair of relatively movable contacts disposedin the upper end of said chamber and normally immersed in said liquid,means operable in response to the initiation of a circuit openingoperation for elongating said chamber so as to form a vacuum in theupper end thereof above the level of said liquid in th regionsurrounding said contacts, and means including a selector unit operableafter a predetermined elongation of said chamber for separating saidcontacts near a current zero point of the alternating current wave.

5. An electric circuit breaker comprising a deiormable substantiallyfluid-tight interrupting chamber, a liquid in said chamber, a pair ofrelatively movable interrupting contacts disposed within said chamber,means operable during a circuit opening operation for deforming saidchamber to increase the volume therein so as to form a vacuum in theregion of said contacts and above the level of said liquid, means forseparating said contacts, and time delay means for preventing theseparation of said contacts until after the establishment of the vacuum.

6. An electric circuit breaker comprising a de- .formable substantiallyfluid-tight interrupting chamber, a liquid in said chamber, a pair ofrelatively movable interrupting contacts disposed within said chamber,means operable during a circuit opening operation for deforming saidchamber to increase the volume therein so as to form a vacuum in theregion of said contacts and above the level of said liquid, means forseparating said contacts, time delay means for preventing the separationof said contacts until after the establishment of the vacuum, andisolating contacts in series with said interrupting contacts andoperable after operation of said interrupting contacts.

7. An electric circuit interrupter comprising a deformable substantiallyfluid-tight interrupting chamber. a liquid in said chamber substantiallyfillinsaid chamber under normal conditions, a pair of relatively movableinterrupting contacts disposed within the upper portion of said chamberand normally immersed in said liquid, means for deforming said chamberso as to increase the volume therein during a circuit interruptingoperation to cause said liquid to vacate the space l 10 within the upperportion of said chamber in the region of said contacts due to the actionof gravity on said liquid, and means for separating said contacts aftersaid liquid has moved out of the region of said contacts.

8. An alternating current electric circuit breaker comprising adeformable substantially fluidtight interrupting chamber, a liquid insaid chamber substantially filling said chamber under normal conditions,a pair of relatively movable interrupting contacts disposed within theupper portion of said chamber and normally immersed in said liquid, aselector unit cooperating with at least one of said contacts andresponsive to instantaneous current through said unit for causingseparation of said contacts under predetermined conditions, and meansoperable during a circuit opening operation of said breaker forelevating the upper portion of said chamber, said contacts and saidselector unit so as to form a vacuum in said chamber in the regionsurrounding said contacts.

9. An alternating current electric circuit breaker comprising adeformable substantially fluidtight interrupting chamber, a liquid insaid chamber substantially filling said chamber under normal conditions,a pair of relatively movable interrupting contacts disposed within theupper portion of said chamber and normally immersed in said liquid, aselector unit cooperating with at least one of said contactssandresponsive to instantaneous current through said unit for causingseparation of said contacts under predetermined conditions, meansoperable during a circuit opening operation of said breaker forelevating the upper portion of said chamber, said contacts and saidselector unit so as to form a vacuum in said chamber in the regionsurrounding said contacts, and a pair of isolating contacts in serieswith said interrupting contacts for isolating the circuit associatedwith said interrupter after operation of said interrupting contacts.

10. An alternating current electric circuit breaker comprising adeformable substantially fluid-tight interrupting chamber, a liquid insaid chamber substantially filling said chamber under normal conditions,a pair of relatively movable interrupting contacts disposed within theupper portion of said chamber and normally immersed in said liquid, aselector unit cooperating with at least one of said contacts andresponsive to instantaneous current therethrough for causing separationof said contacts under predetermined conditions, said selector unithaving a coil disposed with respect to said contacts so as magneticallyto blow the arc drawn between said contacts in a predetermineddirection, and means operable during a circuit opening operation of saidbreaker for elevating the upper portion of said chamber, said contactsand said selector unit so as to form a vacuum in said chamber in theregion surrounding said contacts.

11. An electric circuit interrupter comprising a vertically disposedsubstantially fluid-tight interrupting chamber constructed of deformablematerial, a liquid in said chamber substantially filling said chamberunder normal conditions, a pair of relatively movable contacts disposedin the upper end of said chamber and normally immersed in said liquid,means operable in response to the initiation of a circuit interruptingoperation for elongating said chamber so as to form a vacuum in theupper end thereof above the level of said liquid in the regionsurrounding asaaasc said contacts, means for separating said contactsafter the formation of the vacuum, and magnetic blowout means forblowing the are drawn between said contacts in a direction away fromsaid liquid.

12. In an electric circuit interrupter, a tubular substantiallyfluid-tight interrupting chamber, constructed of deformable material, aliquid in said chamber substantially filling said chamber under normalconditions, means for securing one end of said chamber in position,means for applying a force to the other end of said chamber so as toelongate said chamber and establish a vacuum therein above the leveloisaid liquid, a pair of relatively movable contacts so disposed in saidchamber as to be immersed in said liquid under normal conditions butabove the level thereof when said chamber is elongated, and means forseparating said contacts after elongation of said chamber.

. 13. An electric circuit breaker including a sealed interruptingchamber having relatively separable electrodes disposed therein, aliquid in said chamber means for increasing the size of said chamberthereby to produce a vacuum in said chamber above the level of saidliquid, means for establishing an interrupting gap between saidelectrodes, a common actuating device for operating both saidabove-mentioned means, and

means cooperating with said common actuating device for preventing theestablishment of the gap until after the formation of the vacuum.

14. An alternating current electric circuit breaker including a sealedinterrupting chamber having relatively separable electrodes disposedtherein, a liquid in said chamber, means for increasing the size of saidchamber thereby to produce a vacuum in said chamber above the level ofsaid liquid, means for causing an interrupting gap between saidelectrodes, means for preventing the formation of the gap except whenthe instantaneous current is below a predetermined value, and a commonactuating device for operating said three above-mentioned means.

WILLIAM E. PAUL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Cramblet Dec. 5, 1933

